1. Field of the Invention.
The present invention relates to seal assemblies of the type used to seal between a tubular well conduit and a surrounding conduit and, specifically, to a latching production seal assembly for sealing within the internal bore of a liner within a well.
2. Description of the Prior Art.
Oil and gas wells are completed by installing a production casing or "liner" into the hole from the surface and cementing the liner in place. The liner is typically provided with a setting sleeve having an internally threaded region which is engaged by the external threads of a conventional running tool. The running tool is used to lower the liner to the proper depth within the well, and to apply setting force to "hang" the liner from gripping members within the well bore.
After the liner has been hung and cemented in place, the liner is perforated at the producing depth and the oil and/or gas flows from the surrounding earthern formation through the perforations and up the liner to the surface, usually through production tubing.
In the past, production seal assemblies have generally included a latch mechanism with radially moving dogs which latched into a circumferential groove provided in a joint of the liner or extension thereof. The latch mechanism anchored the seal assembly in place and provided a sliding and sealing action which permitted the attached tubing string to lengthen or shorten due to pressure and temperature changes in the well bore during operation of the well.
The radially moving dogs utilized in prior latch mechanisms of the above type presented a possible problem area, since sand and other contaminates could impede the action of the dogs. In addition, the provision of a circumferential groove in the surrounding well conduit required additional milling and the presence of the specially designed pipe sub in the liner string which was to receive the seal assembly and latch mechanism.
The present invention has as its object the provision of a retrievable production seal assembly which can be latched into the internally threaded surface of the liner setting sleeve. These are the same threads which are engaged by the liner running tool during the installation of the liner within the well bore and prior to retreiving the running tool to the well surface.
Another object of the invention is the provision of a latch mechanism for latching into the liner setting sleeve threads which eliminates the need for radially moving dogs.
Another object of the invention is the provision of a seal assembly which allows a straight pull release as a safety measure in addition to a standard release effected by right hand rotation of the tubing string from the well surface.